1. Field of the Invention
The present invention relates to 1,4-dihydropyridine derivatives, salts thereof, a process for the preparation of same as well as a pharmaceutical agent comprising at least one of the compounds and salts, as an effective ingredient.
2. Related Arts
It has been know that certain kind 1,4-dihydropyridine derivatives have a powerful calcium antagonistic effect and thus can be employed as an effective ingredient for curing blood circulatory diseases.
As one of exemplar known 1,4-dihydropyridine derivatives, dimethyl ester of 1,4-dihydro-2,6-dimethyl-4-(2-nitropheny)pyridine-3,5-dicarboxylic acid (known as --Nifedipine--) may be listed. This compound has pharmaceutical activities of coronary vasodilating action, blood pressure depressing action and the like [W. Vater et al "Arzneim.-Forsch" (Drug Res.), Vol. 22, page 1, 1972]. As another exemplar known compound, 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-pyridine-3,5-dicarboxylic acid 3-2-(N-benzyl-N-methylamino)ethyl 5-methyl ester (known as --Nicardipine--) may be listed, which has a cerebral blood flow increasing action.
Among the both known compounds, the Nifedipine shows a powerful depressing action but as a result, has a tendency of causing a relative decrease on cerebral blood flow. On the other hand, the Nicardipine having the cerebral blood flow increasing action, has been developed and clinically employed as one of cerebral circulation improving agents but it can not be said as it selectively acts to the cerebral blood path to increase only the blood flow therein.